Did you check your Throttle position sensor, (TPS) although it sounds like a bad AFM. If the TPS is bad, you cant set your timing, and it sounds like your timing is off, but since it ran OK with the AFM disconnected, even for a second I would guess that is it. Maybe you can try to swap it with another to check it out?

I had some really rough idle and replaced all of my seemingly good vacuum hoses, and that made a big difference.

I am sure there are ohm meter tests for the AFM same as the TPS, check the FSM

Sold Truck: 89 DLX extra cab 4x4 22re Automatic/ New truck 97 T100 4x4 auto Sr5